The conventional tape remaining time display system generally employs a system which performs a calculation for each predetermined number of rotations of a supply-side reel in response to a pulse output from the reel during a constant speed travel of a length of tape, for example. Thereby, the current length of time of the length of the remaining tape is successively calculated and displayed.
During recording or reproduction, the cycle of the reel varies depending on the amount of turns for the length of tape around a reel. The extent of such variations is a few second, for example, 6 seconds at the start of the winding and 3 seconds at the end of the winding. If the calculation is performed for each rotation of the reel having such a cycle, the length of time which is descriptive of the length of the remaining tape can be calculated in the order of a few seconds.
The length of time which is descriptive of the remaining length of tape employs a system wherein the display is updated each time the calculation is performed.
Accordingly, the relationship of the calculated value and the displayed value of both of the length of time, which is descriptive of the remaining length of tape and the displayed value relative to the passage of time, is illustrated in FIG. 5.
Referring to FIG. 5, assuming that the length of time descriptive of the remaining length of tape calculated at, for example, the timing t1 is expressed by C1, the value thereof is continuously displayed up until the timing t2 as illustrated by the single-dotted chain line or only the display is varied as illustrated by the solid line. If the length of time descriptive of the remaining length of tape calculated at the timing t2 is expressed by C2, the value thereof is displayed as illustrated by the single-dotted line or the solid line in a manner similar to that described above. Thereafter, the length of time which is descriptive of the remaining length of tape is similarly displayed. It is to be noted that the timings t1, t2 . . . are employed in the form of the timing for each rotation of the reel.
Because the conventional tape remaining time display system is so constructed as hereinabove described, the result of the calculation is adversely affected by fluctuations in the tape winding when the length of the tape is tightly wound or loosely wound. For example, fluctuations in the rotation of the reel such as woof and flutter, and errors in the measurement of the reel rotation cycle tend to be displayed. Therefore, there is a problem when an error is relatively large and a discontinuity tends to occur in the display of the length of time, which is descriptive of the remaining length of tape, in such a way that the display of the length of time, which is descriptive of the remaining length of tape, may jump back and forth.